1. Field of the Invention
The present invention relates to a system and method for monitoring vital signs and capturing data from a patient remotely using telemonitoring techniques. In particular, the present invention is a low cost, patient-friendly, ambulatory monitoring system incorporating a low cost memory card or smart card for the remote electronic capture of noninvasive vital signs data including, e.g., full single or multiple lead ECG, respiration rate, SpO2, skin temperature, and blood pressure.
2. Description of the Prior Art
Before drugs and related therapies are approved for widespread use by physicians, such drugs and therapies typically undergo numerous trials for efficacy and safety. Successful human trials are critical to regulatory approval of a new drug or therapy, and accordingly, much money and effort goes into the human trials. At present, patients are selected for the trial and placed on the regimen under test. The efficacy and safety of the drug and/or therapy is tested by having the patient make numerous visits to his or her physician for testing during the trial period. While a great deal of information can be gathered at such tests, generally there is no method for collecting the data between physician visits, thereby causing decisions regarding efficacy and safety to be made base on a small sampling of the patients"" experiences with the drug and/or therapy. More frequent visits to the physician would improve the data pool; unfortunately, such visits are expensive, add to the overall cost of the trial, and, because a limited data set is available, the trial duration is lengthened, thereby delaying the drug""s market introduction.
An improved technique for testing the efficacy and safety of a drug and/or therapy is desired which does not require additional visits to the physician. It is desired to develop a technique for collecting data from a human subject at all times during a trial without requiring any visits to the physician""s office, thereby eliminating the cost and inconvenience of visiting the physician""s office for routine monitoring.
Also, an improved remote patient monitoring/management system is generally desired whereby useful vital signs data may be obtained from a patient without requiring frequent visits to the physician""s office. Such remote monitoring/management is particularly desirable for home patient monitoring of patients with chronic illnesses such as congestive heart failure or for post-operative or out-patient monitoring. Prior art patient telemetry systems have had limited commercial success for a variety of reasons such as difficulty of use and cost.
Remote patient monitoring techniques are generally known in which electrodes are placed on the patient to monitor the patient""s vital signs and the captured data is transmitted to a remote display for monitoring the patient""s condition. Remote monitoring systems are known which permit a doctor or nurse to monitor the conditions of several hospitalized patients from a central monitoring site in the hospital. Typically, sophisticated patient monitoring equipment is used to collect data from the patient, and the collected data is transmitted via wire to the central monitoring site in the hospital. Generally, wireless systems are problematic in the hospital setting because of the proximity of the respective patients and the amount of interference found in such a setting.
Most of the patients receiving a particular drug regimen or therapy being tested are ambulatory and, in many cases, participating in the study from home. Remote monitoring of patients from their homes introduces an entirely new set of challenges for transmitting the gathered data to a central location for evaluation. Numerous attempts have been made to facilitate such data collection and transmission; however, in each case, cumbersome and uncomfortable monitoring equipment is placed on the patient and the patient is tethered to the monitoring equipment by electrical cords, thereby limiting the patient""s movement. In some prior art systems, the electrical cords have been removed and the transmissions to the monitoring equipment made using telemetry techniques; however, such systems have been used primarily for real-time vital signs monitoring and not for data collection of the type needed for diagnosis and efficacy and safety testing. Moreover, such systems also limited the movement of the patient to a limited area near the vital signs monitor.
For example, an early telemetry system is described in U.S. Pat. No. 3,603,881 in which short transmission distances to a building""s wiring system are covered using VHF transmission. Physiologic data such as electrocardiographic (ECG) data is collected by a sensor and transmitted by a VHF transmitter to a fixed VHF receiver RF transmitter coupled to the wiring system in the building. A RF receiver demodulator monitor is coupled to the building""s wiring system at the nurse""s station for receiving the physiologic data for patient monitoring and/or data recording.
A similar telemetry system for monitoring ECG signals is described in U.K. Patent Application No. 2 003 276 except that telephone connections are used in place of the building wiring and the system is also designed to collect blood pressure, pulse rate, respiratory rate and the like and to relate that information to the physician via the telephone connections.
Other early telemetry systems of the type described by Lewis in U.S. Pat. No. 3,943,918 and by Crovella et al. in U.S. Pat. No. 4,121,573 use telemetric techniques to transmit data from a sensor device attached to the patient""s chest via RF to a radio telemetry receiver for display and/or recording as desired. S. S. Ng describe yet another telemetry system for ECG monitoring in an article entitled xe2x80x9cMicroprocessor-based Telemetry System for ECG Monitoring,xe2x80x9d IEEE/Ninth Annual Conference of the Engineering in Medicine and Biology Society, CH2513-0, pages 1492-93 (1987). Ng therein describes a system for providing continuous ECG monitoring and analysis by means of a PC AT via wireless link. In the Ng system, the patient requires a transmitter that is carried by the patient for sensing and transmitting the patient""s ECG signal to a central base station via wireless link. At the base station, a receiver recovers the original ECG signal from a few patients simultaneously for display.
Each of the above-described telemetry systems is designed primarily for hospital use and include relatively expensive sensor arrays and processing devices for real-time patient monitoring and diagnosis. The real-time monitoring is generally used in an xe2x80x9calarmxe2x80x9d mode to capture events, rather than to collect data over a period of time to determine trends which might indicate a more gradual deterioration or improvement in the patient""s condition or to predict a forthcoming event. Also, these systems require the patient to remain in close proximity to the base stations including the receivers.
Bornn et al. describe a portable physiological data monitoring/alert system in U.S. Pat. Nos. 4,784,162; 4,827,943; 5,214,939; 5,348,008; 5,353,793; and 5,564,429 in which a patient wears a sensor harness including a microprocessor that detects potentially life-threatening events and automatically calls a central base station via radiotelemetry using a radio modem link. In a home or alternate site configuration, communications between the base station and remote unit is by way of commercial telephone lines. Generally, the system automatically calls xe2x80x9c911xe2x80x9d or a similar emergency response service when an abnormality is detected by the ECG monitor. Unfortunately, the sensor harness is quite cumbersome and conspicuous and includes sensors for performing an alert function rather than data collection and analysis functions.
Segalowitz discloses a wireless vital signs monitoring system in U.S. Pat. Nos. 4,981,141; 5,168,874; 5,307,818; and 5,511,553 including aprecordial strip patch including a multi-layer flexible structure for telemetering data by radio frequency or single wire to hardware recording apparatus and a display monitor. Microsensors and conductive contact elements (CCEs) are mounted on the strip patch so as to permit simultaneous and continuous detection, processing and transmission of 12-lead ECG, cardiac output, respiration rate, peripheral blood oximetry, temperature of the patient, and ECG fetal heart monitoring via a single wavelength of radio frequency transmission. While the precordial strip patch used by Segalowitz purportedly transmits vital signs data up to 50 meters, it requires a dual-stage operational amplifier chip, an encoder modulator chip, a wireless transmitter chip including an oscillator, and other costly components such as artificial intelligence software, sound and visual alarms, and a microprocessor. As a result, the precordial strip patch is relatively expensive to manufacture and operate. Also, as with the other telemetry systems noted above, the emphasis of Segalowitz is on real-time monitoring and alerting of medical personnel to immediate medical needs of the patient.
Platt et al. also disclose a sensor patch for wireless physiological monitoring of patients in U.S. Pat. No. 5,634,468. Platt et al. describe a sensor and system for monitoring ECG signals remotely from patients located in non-hospital sites. In this system, a sensor patch containing sensing electrodes, signal processing circuitry and radio or infra-red transmission circuitry is attached to the patient""s body and preferably worn for at least a week before its power supply is exhausted and the sensor patch is thrown away. A receiver at a primary site in the vicinity of the patient receives the data transmitted by the sensor patch and stores the sensed data. When the patient feels discomfort or concern, or if the portable unit sounds an alarm, the patient telephones the monitoring station and downloads the stored data from the portable unit via the standard voice telecommunications network. The downloaded ECG data is then monitored and analyzed at the monitoring station. The receiver in the proximity of the patient may be a portable unit carried around by the patient, where the portable unit includes a receiver, a processor for processing the received data to identify abnormalities, a memory for storing the sensed data, and circuitry for interfacing to a telephone line to send the ECG data signals to the monitoring station. The monitoring station decodes the received ECG signals and performs beat and rhythm analysis for classification of the ECG data. If an abnormal condition is discovered, medical personnel in the vicinity of the patient are contacted. While the system described by Platt et al. may collect ECG data from the patient and process it at a remote monitoring station, the data is only collected when the patient initiates the data download. Otherwise, data is lost once the memory in the portable unit is full. No mechanism is provided for continuously collecting data, at all times, in a way which requires little or no patient action.
In U.S. Pat. No. 5,522,396, Langer et al. disclose a telemetry system for monitoring the heart of a patient in which a patient station includes telemetering apparatus for transmitting the outputs of patient electrodes to a tele-link unit connected to a monitoring station by telephone lines. As in the Platt et al. system, Langer et al. transmit ECG data to a central location. However, unlike the Platt et al. system, the Langer et al. system checks the ECG data for predetermined events and automatically calls the monitoring station when such events are detected. A similar telemetry system is described by Davis et al. in U.S. Pat. No. 5,544,661 which initiates a cellular phone link from the patient to the central monitoring location when an event is detected. As with the Platt et al. system, the Davis et al. system does not provide a mechanism for continuously collecting data with little or no patient action.
Accordingly, a telemonitoring system is desired which collects vital signs data from a patient using an inexpensive device that permits the continuous collection of a patient""s vital signs data with little or no patient action. Also, a data management system is desired which permits the collected data to be reviewed and formatted for use in patient trials and the like. The present invention has been designed to meet these needs in the art.
The present invention meets the above-mentioned needs in the prior art by providing a portable remote patient telemonitoring system which collects vital signs (health parameter) data from a patient using a disposable sensor device attached to the patient and stores the vital signs data on a memory card or a smart card that may be inserted into the sensor device for data collection and/or transmits the data to a portable data logger or base station unit for processing and storage. In a first embodiment, a memory card is used that stores the vital signs data and is removed and its contents downloaded to a monitoring device for performing processing and monitoring functions. In a second embodiment, the electronics of the disposable sensor device are provided on a removable smart card-type device that may or may not have memory for storing the collected vital signs data. The electronics on the smart card may or may not include transmission circuitry for transmitting the vital signs data to a nearby portable data logger or a base station unit. Each embodiment of the portable remote telemonitoring system in accordance with the invention is characterized by combinations of the following separate elements, each with different functions within the system.
The first component is an adhesive, cordless, disposable sensor band with electrode patches, other sensors, and a connector dock for accepting a conventional memory card, such as an MMC memory card, for storing detected vital signs data, or a smart card that contains electronic circuitry and may or may not contain memory. Additional internal memory equivalent or discrete memory may also be available on the memory card or smart card. The smart card preferably includes the sensor band""s electronics so that the cost of the disposable sensor band may be minimized. The sensor band is easy-to-use and is positioned on the patient by the patient. The sensor band is designed to be worn comfortably by the patient for 24 hours, at which time the sensor band may be discarded and replaced by a new sensor band. The memory card or smart card is ideally designed to store all vital signs data generated by the patient during that 24 hour period. The memory card or smart card is removed from the sensor band before the sensor band is discarded, and the memory card or smart card is either mailed or carried to a remote monitoring station or, more preferably, inserted into a base station which uploads the stored vital signs data to the remote monitoring station. Since the vital signs data is collected on a memory card or smart card received in the sensor band, the patient is free to move around freely while his or her vital signs are being monitored. Once the data stored on the memory card or smart card is uploaded, the memory card or smart card may be used again with another sensor band.
The second component is a base station having a memory card/smart card reader for accepting the memory card or smart card, reading the vital signs data stored therein, and storing the vital signs data until the stored data is to be uploaded via conventional phone lines to a remote monitoring station. The base station may also be designed to capture additional clinical data, such as blood pressure data, to perform data checks, and to process the stored data. For data transfer, the base station connects the memory card or smart card, via modem and land or cellular telephone line, to the remote monitoring station. Connections for auxiliary sensors such as a blood pressure cuff extend the number of clinical parameters that can be captured. Patient safety is enhanced by the ability of the base station to compare clinical data, e.g. ECG, against given profiles and to indicate violation of preset limits when appropriate or when the base station is programmed to do so. Such violations could be indicated to the patient by audio and/or visual indicators.
The third component is a remote monitoring station that allows the presentation and review of data (including event flags) forwarded by the sensor band and other sensors and simply requires a standard PC running, e.g., Windows NT. ECG analysis software and a user-friendly graphical user interface are provided to remotely analyze the transmitted data and to permit system maintenance and upkeep.
In a preferred embodiment, the patient health parameter data collection and monitoring system of the invention is characterized by a sensor band having a sensor assembly for application to a subject, where the sensor assembly produces health parameter data indicative of values of at least one health parameter of the subject. The sensor band in accordance with the invention includes a connector that accepts a memory card, such as a low cost MMC memory card, that includes internal memory for storing the health parameter data produced by the sensor band, or a specially designed smart card that contains the signal processing circuitry (ADC, etc.) as well as any desired memory. The memory card or smart card is then removed and inserted into a monitoring station including a memory card/smart card reader which is adapted to read the health parameter data from the memory card or smart card for display or further processing. The memory card or smart card may be taken or mailed to a remote monitoring station for data download, or, conversely, the memory card or smart card may be inserted into a base station at the patient""s location for uploading the health parameter data from the memory card or the smart card to the remote monitoring station via a telecommunications link. The remote monitoring station captures the vital signs data and stores it in a database for display and subsequent access. The remote monitoring station also processes the health parameter data for medical diagnosis or analysis. In the preferred embodiment, the remote monitoring station stores the health parameter data in the database with the vital signs data from a plurality of other patients. A user interface provides access to the vital signs data in the database for processing, medical diagnosis and/or analysis.
As noted above, the smart card also houses the sensor band""s electronics so that the electronics may be reusable from one sensor band to the next. Such electronics may include a rechargeable power supply that is recharged when the memory card or smart card is inserted into the base station unit for data download. Alternatively, the power supply may reside on the sensor band (e.g., in the smart card/memory card connector) and be discarded with the disposable sensor band when the power supply is depleted.
In presently preferred embodiments, the sensor band measures full waveform single or multiple lead ECG, full waveform respiration, skin temperature, and motion and stores the measured data in the memory card or smart card. Auxiliary sensors are preferably provided at the base station, such auxiliary sensors including, e.g., a blood pressure cuff, a spirometer, and weight scales. Also, the user interface at the remote monitoring station may contain full ECG analysis software covering waveform measurements, interval measurements, beat-typing and arrhythmia detection. xe2x80x9cEvent flagsxe2x80x9d also may be generated and indicated to the physician for high and low heart rate, high and low respiration rate, high and low temperature, high and low blood pressure or arrhythmias.
While there are many potential patient management applications for the remote telemonitoring system of the invention, such as remote measurement of cardiovascular abnormalities including hypertension, congestive heart failure, arrhythmia, silent ischaemia, and the like, and respiratory abnormalities including chronic obstructive pulmonary disease, in a presently preferred implementation of the invention, the remote telemonitoring system of the invention is also designed to reduce both the length and the cost of clinical drug trials by providing versatility in data collection with respect to site (in-clinic or domiciliary), time, and volume, and to provide direct, electronic data capture. Additional applications include the monitoring of sleep apnea, diabetes, acute or sub-acute infection, asthma, and the like, as well as xe2x80x9cremote nursexe2x80x9d applications which provide a live view of the patient""s condition. However, those skilled in the art will appreciate that the use of a memory card or such a smart card is not well-suited to real-time vital signs monitoring unless the smart card includes transmission circuitry. Such transmission circuitry is included in another embodiment of the invention whereby the smart card includes transmission circuitry for broadcasting the vital signs data to a portable data logger or base station unit for remote storage. In such an embodiment, the smart card may or may not contain memory for storing the vital signs data and may or may not include the sensor electronics. However, the inclusion of some memory on the smart card is preferred as it may act as a buffer in the event that the transmission channel with the portable data logger or base station unit is lost for some reason (e.g., the sensor band is out of range).
Though generally applicable to patient home use, those skilled in the art will appreciate that the system of the invention also may be used in a clinic or hospital setting. Corresponding methods of collecting a patient""s vital signs data using the remote telemonitoring system of the invention are also described and claimed herein.